It could take months to know the cause of the South Florida building collapse. For now, officials are focused on finding dozens who are unaccounted for

Two days after the catastrophic partial collapse of a residential building in South Florida, officials remained focused on the search for the dozens of people believed to be under the mountain of rubble as an expert suggested it may be months before the cause of the disaster is known.

While anxious family members awaited some news -- and the search continued through the night -- officials urged for a powerful sentiment: Hope. "I am holding out hope because our first responders tell me they have hope," Miami-Dade County Mayor Daniella Levine Cava told CNN. "They are the ones on the ground. They are in the tunnels; they're in the water; they're on top of the rubble pile. They're helping to sift through using the cameras, the dogs, the sonar, and they say they have hope."